Preparation of Bi-based photocatalysts in the form of powdered particles and thin films: A review

Bismuth-based semiconductors, as an emerging group of photocatalysts possessing a layered-structure, have been widely demonstrated to show excellent photo-oxidation capability in water oxidation and pollutant decomposition. Deriving from the suitable band gap and well-dispersed valence band, Bi-based materials are generally visible-light-responsive and consequently have received considerable interest in photocatalysis. Different from conventional binary metal oxide semiconductors, the synthesis of Bi-based materials needs to be carefully controlled as most of them are prepared as ternary oxide materials that comprise multiple elements and are sensitive to the synthesis conditions. Specifically, different methods need to be employed to obtain suspended particles and electrodes for photocatalytic and photoelectrochemical reactions, respectively. Given that the synthesis process for photoelectrodes usually involves more than one step, fabricating the desired ternary Bi-based photoelectrodes can be more challenging when compared to powdered photocatalysts. With the significant emergence of Bi-based materials, understanding the effect of different synthesis methods on the catalyst properties is crucial to ensure great performance. This review summarizes recent developments in Bi-based photocatalysts by comparing and discussing various synthesis approaches for powdered photocatalysts and thin film photoelectrodes.